Solved! Go to Solution.
I had this problem and here is a fresh solution to it. Had problems with sharing the actual connection though, it did not recognize me as an owner for some reason but I found a workaround for that below:
1. Follow video https://youtu.be/ROKO589RBnQ
2. Attempt to share connection to someone/grp, save your user GUID.
3. Create instant flow with these steps (actually I did not need Get Custom Connectors as Admin) on an admin account in the environment:
From the out data of "Get connections as admin", CTRL+F your connection name and in $connection variable, you can find apiId: "/providers/microsoft.powerapps/apis/_your custom connector ID_"
Copy last ID which is your Connector Name for last step in flow.
Environment name is the one when you browse https://make.powerapps.com/environments/_Environment name_ so copy last bit there.
4. Fill in CanEdit in put Role Name and put Principal Object ID, fill in your user GUID that wants to be able to share connection.
5. Run flow.
You now should be able to share the connection without errors. Worked for me atleast!